For reasons of aesthetic appearance and of quality, in order to make the various portions of an article, it is necessary to choose pieces of appearance that is similar to degrees that vary, in particular as a function of their proximity and of their locations in the article.
For example, for leather, and in particular for a leather sofa, a high degree of similitude in appearance is sought between the pieces forming each seat back, between the pieces forming each seat cushion, between the seat backs, between the seat cushions, and between each seat back and each corresponding lumbar support cushion. However, a lower degree of similitude can be accepted between seat backs and seat cushions, between armrests and seat backs, and between armrests and seat cushions. A lower degree of similitude is also acceptable for the pieces serving to trim the structure of the sofa, both between said pieces, and between them and the other pieces.
Unfortunately, leathers, and in particular natural leathers, are not uniform in appearance and quality. That applies not only to different hides, even when they come from the same batch, but also to any one hide. Variations in color shade, grain size, and leather quality can be observed between different zones of the same hide, and, within any one zone, the appearance can vary, e.g. between matt and glossy, depending on the angular position of the hide relative to an observer. That applies regardless of the origin of the leather.
For natural leathers, the layout of the component pieces of an article must therefore satisfy certain constraints. In addition, any flaws must be taken into account. Depending on their seriousness, such flaws can preclude the use of certain zones of the leather, or restrict such use to pieces which can accept such flaws, e.g. because of their locations in the final article. To a lesser degree, such a requirement to satisfy constraints also exists for leathers that are not totally natural, e.g. pigmented leathers which are of uniform color, or corrected leathers or flesh splits that have been embossed to give a grain effect, after buffing or splitting.
Currently, and in particular for laying out pieces for high-quality articles of furniture or upholstery, the task is entrusted to the know-how of an operator capable of ensuring that all of the constraints are satisfied.
It is desirable to have a method making it possible to perform such laying out automatically, so as to avoid the need for laying out to be performed by an operator, and so as to optimize layouts better in order to waste as little as possible of a costly raw material.
Proposals have been made to automate laying out on leathers.
German Patent DE 195 21 514 describes a method comprising digitizing the outlines of the hides and detecting flaws organized into various categories with which different colors are associated. Laying out is performed either by an operator on the basis of an image showing the outline of the hide and the colored flawed zones, or else automatically by implementing suitable software.
A similar method is described in U.S. Pat. No. 5,258,917, the layout taking account of a possible additional constraint, namely the desirable proximity on a hide of portions of outlines of different pieces.